1. Field of the Invention
The invention relates to a delay circuitry for battery protection, particularly to a circuit having functions of automatically choose one from between an inner delay and external delay according to the requirement.
This application claims priority from Taiwanese Application No. 094143045, filed Dec. 6, 2005.
2. Description of the Prior Art
Generally, a battery is the only power source for all kinds of mobile electronic apparatus. With the popularity of the mobile phone, Notebook computer, personal digital assistance (PDA), MP3 player, the reliance on battery is significantly increased. The handheld appliance goes to have characteristic of light, slim, short, and small but has multi-functions are often preferred, to solve this dilemma, decrease the power consummation of the integrate circuit and increase the cell capacity become necessary.
Li-ion cell is known to have such characteristic: small volume, high charge capacity, without memory effect, long life, low discharge ability by itself, thus trying to capitalize the Li-ion cell as main power of the mobile device with chargeable cell is a wave that can not be blocked. As alike as material properties of Ni—Cd cell or Ni—H battery does, it has to be taken charge and discharge of the battery into account to prevent them from material degradation so as to have better performance. Particularly, for the Li-ion battery, it often has a battery protective circuit because it has the highest unit cost among them. Improper over discharge or overcharge or even overcurrent to a battery, is readily to cause the battery lifetime shortening.
Similar to a chip control, a battery protective circuit has to filter out those probable noises so as to avoid inducing malfunction, such as overcharge or overdischarge. The noises induced typically are due to a ripple voltage over the detecting threshold during switching. Hence, a delay circuit is designed in the battery protective circuit for this purpose. Only those pulse extended over the delay time are taken as a signal, or it will be taken as a noise and will be neglected. The conventional approaching to the time delay for battery protective circuit is implemented by an external capacitor which is connected to a pin COL of the battery protective IC. The capacitor can be replaced with an appropriate capacitance in accordance with the requirement. Some of cases are done by using internal signal because the delay is usually fixed and can't be adjusted as easy as an external capacitor. However, even the time delay is fixed, the internal delay signal is usually enough to apply to most of the requirements. Besides one of external components, an external capacitor, can be removed. Even though, clients are often favor a battery protective IC provided with an external delay therein for choice.
An object of the present invention thus provides a battery protective IC, which automatically chooses an internal delay signal as a delay time when the pin COL is floated and the delay time determined by a capacitor when the capacitor is connected with the pin COL.